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## [TowerTalk] Antenna surface area

 To: [TowerTalk] Antenna surface area n3rr@erols.com (Bill Hider) Sun, 10 Jun 2001 02:13:08 +0100
 ```The formula Gene proposed is not exactly correct, nor does he precisely state what to do with the taper. Regarding the formula, Gene's thinking is: If you think of the wind as hitting the tube broadside (at 90 Deg to the tube), the exposed surface area as seen by the wind looks like a rectangle whose length is the length of the tube and whose height is the full OUTSIDE diameter of the tube. Hence, L x Dia. Unfortunately, it is not that simple. The tube is a cylinder as seen by the wind, hence the angle that the wind *hits* the tube, even if it is perpendicular to the tube, hits at 0 Deg on the centerline and then the angle increases to 90 Deg as the wind hits the tube away from the centerline (above and below the centerline of the tube for a horizontal element). This assumes the wind-front is wider than the outside diameter of the tube, which is probably a very good assumption. So, the surface area exposed to the wind by the tube is not simply L x Dia. It's the exposed tube length times the integral from 0 to Dia of the surface area of each tube (Pi x Dia), where Dia is the Outside diameter of the tube. Gene, this is why the manufacturer's wind area is less than what you calculated, and theirs is correct. [If anyone has trouble picturing this, let me know and I'll try to explain it in more detail.] But, I question the correctness of adding all of these calculations up and saying that's the *wind area*. It certainly is the 1/2 of the *surface area* if it's done this way, but the wind cannot be simultaneously hitting the elements at 90 Deg and the boom at 90 Deg, so it should take that into account by specifying the *larger* of both calculations, but not the sum of both. Regarding the taper: each tube should be calculated separately for the *exposed* length of the tube *only*. Remember, some tubes are *inside* other tubes, causing the taper. Bill, N3RR ----- Original Message ----- From: Stu Greene To: EUGENE SMAR ; Sent: Sunday, June 10, 2001 2:42 AM Subject: Re: [TowerTalk] Antenna surface area > At 09:06 PM 6/9/01 -0400, you wrote: > > > Area = L X diameter for the exposed surface of each piece of aluminum, > > simple as that. > > > > Shouldn't the calculation be L X (Diameter X pi) ? Or length times > circumference? > > And this doesn't reflect tapering of the elements. > > > List Sponsor: Are you thinking about installing a tower this summer? Call us > for information on our fabulous Trylon Titan self-supporting towers - up to > 96-feet for less than \$2000! at 888-833-3104 > www.ChampionRadio.com > > ----- > FAQ on WWW: http://www.contesting.com/FAQ/towertalk > Submissions: towertalk@contesting.com > Administrative requests: towertalk-REQUEST@contesting.com > Problems: owner-towertalk@contesting.com > List Sponsor: Are you thinking about installing a tower this summer? Call us for information on our fabulous Trylon Titan self-supporting towers - up to 96-feet for less than \$2000! at 888-833-3104 www.ChampionRadio.com ----- FAQ on WWW: http://www.contesting.com/FAQ/towertalk Submissions: towertalk@contesting.com Administrative requests: towertalk-REQUEST@contesting.com Problems: owner-towertalk@contesting.com ```
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